This seems a (surprisingly) reasonable and modest request:
I’d like to see what the law is in other states, but the union arguments sound a lot like grasping for straws to keep non-union laborers out of construction.
Counterpoint: Contractors and property owners insure themselves against these suits, giving them a fixed monthly cost. This cost can be passed onto the workers in the form of lower wages, in essence, evening out the “blame” for accidents. The employer is also in a better position to train workers and to erect scaffolds (and other safety structures).